No issues from mine yet on the latest firmware.

Still no auto config backup to USB yet though

Hello, 120 users, 100/100 WAN (Huawei microwave link), heavy internet use, more than 200 devices (incl workstations, laptops, mobiles via 4xUbiquity AC AP Pro in two floor office), about 10-20 vpn remote users= 31 Days Uptime.
I declare this product stable
https://postimg.cc/TKsc6kyp

Coming up to 1000 hrs without a reboot a first but then I haven't done any config changes.

1061 hrs for me with some config changes

Spoke too soon the 1000hr run came to abrupt halt after I edited a few bind ip to mac address. A few hours later access to ipv4 web sites failed while sites that used ipv6 were fine. Internal network was fine of course. A reboot was needed to fix this.

I am on 1240 hrs, heavy use with 120 users, some changes (mostly additions of VPN users) and still running perfectly ( I have counted over 250 devices in 3 LANs)
I admit though, I am on leased microwave link with no IPv6.

I would certainly contact support for your case, this little monster needs some caring

Hopefully it will catch up to the 264 days of my 3900 (with 3 VDSL 200/20)
https://postimg.cc/87sv5zwx